Unraveling the diverse grazing effects: Examining the variations in spatial patterns of soil microbial diversity across dimensions, Kingdoms, and depths in Tibetan grasslands

Changes in soil microbes have profound effects on ecosystem stability. However, the effects of grazing on soil organisms, particularly their spatial distributions, are still unclear in grasslands. We investigated the responses of the three dimensions (taxonomic, functional, and phylogenetic) of α- and β-diversity, along with the community composition of two Kingdoms (fungi and bacteria), to grazing in the Xizang's grasslands. Here, α-diversity referred to the diversity within a single microbial community, which was measured across taxonomic, functional, or phylogenetic dimensions under either fenced or grazing conditions at a particular site. β-diversity represented the differences in taxonomic, functional, or phylogenetic composition either between two sites under the same conditions or between fenced and unfenced areas within the same site. The overall effects of grazing on soil microbes depended on the dimensions, Kingdoms and depths across all sites. For instance, at 0–5 cm, grazing increased the functional Shannon α-diversity of bacteria but not fungi. Responses of soil microbes to grazing showed clear spatial patterns, and these responses also varied with soil depth, microbial Kingdoms, and diversity dimensions. These response patterns were determined by differences in the relative influence of the three assembly processes (similarity, richness difference, and replacement), as well as by shifts in predominant environmental variables. Therefore, in the future protection of soil microbial diversity, the three dimensions of taxonomy, function, and phylogeny should be considered simultaneously. Meanwhile, more attention should be paid to the α-diversity of soil bacteria rather than soil fungi. In terms of soil microbial diversity protection, fencing is not always effective.